Currently available HF shunt antennas, which have been installed on the leading edge of a vertical stabilizer in most Air Transport Aircraft for the past forty years, have worked very well when used in conjunction with a HF coupler (ex.—an impedance tuner). However, upon installation on composite-bodied aircraft (where minimal conductive material is present in the vertical stabilizer), these currently available HF shunt antennas (which were previously spec-compliant) begin to present impedance curves that are nearly impossible for Commercial Off-The-Shelf (COTS) HF couplers (ex. —RCI CPL-920D) to tune. This is due to a lack of conductive material around the HF shunt antenna and reduced coupling between the HF shunt antenna and the aircraft structure, which reduces radiation resistance and increases the Q (ex. —increases the reactance of the HF shunt antenna) and the equivalent parallel resistance (Rp) of the HF shunt antenna. A traditional approach to improving Rp in an HF shunt antenna has been to increase the length of the HF shunt antenna. However, this is of limited effect and often requires an unacceptable increase in the HF shunt antenna's footprint.
Thus, it would be desirable to provide an HF shunt implementation which obviates the problems associated with currently available HF shunt implementations.